High-voltage, high-power RF signals, as employed for example in the field of broadcasting for communication and entertainment, are often coupled from transmitters, which are typically located at ground level or otherwise made readily accessible for maintenance, for distances up to thousands of feet to reach the antennas from which the signals radiate.
This coupling process usually takes place using rigid coaxial lines (coax) made from concentric pieces of tubing, spaced with insulators, carefully dimensioned and finished, assembled, sealed, and often pressurized, typically with aggressively dried air or with nitrogen gas that has been purged of water vapor, oxygen, and other contaminants to the greatest extent possible. Individual sections of coax, which may be from an inch or less up to a foot in diameter depending on the level of power carried, are typically joined end to end to each other and/or to other equipment using specialized connectors or couplings.
Where space is not at a premium, it is often possible to use the standard fittings that were developed and adopted by the Electronics Industry Association (EIA) as EIA-225 some decades ago. These fittings are generally standardized and interchangeable. However, for some applications, space can be critical, and for such circumstances the known fittings can be undesirably bulky. For example, some prior art devices employ radially projecting flanges joined by longitudinal bolts. The radial projection dimension can be significant, due to clearance for bolt heads and tool heads that drive the bolts. In the prior art, there is no suitable reduced-dimension substitute among EIA-225 standard RF power fittings.
Accordingly, there is a need in the art for an RF power coaxial coupling outer fitting that provides the capability for reduced size, reduced element spacing, and/or increased packing density when compared to conventional designs, while retaining RF performance that is essentially identical to conventional designs and mechanical strength that achieves a level of performance suitable for useful applications.